Meat products, such as salamis, hams, poultry, turkeys and sausages are often encased in double casings comprising a film and a net. The encasing, or stuffing process comprises pushing the meat product through a meat stuffing horn and applying a double casing over the meat product. The meat product may be fresh or processed meat. The double casing comprises an inner film with an outer netting. The inner film layer is primarily used to contain the meat and give it a desired shape (eg sausage shape), as well as assisting to protect and preserve the meat, and may be edible or inedible, and made of synthetic or natural materials. The outer netting may be knitted, woven, extruded or otherwise manufactured and may be rigid or elastic, and typically applies compressive force on the meat to assist in curing and/or preservation of the meat (eg by forcing out any air), or to apply a surface pattern to the meat to give it a desirable appearance.
Typically the netting is stored and shipped in a loose unstretched form. In preparation for use, the netting is shined onto a casing tube so that the netting is arranged in tight folds on the casing tube. The diameter of the casing tube is slightly larger than the diameter of the meat stuffing horn so that the casing tube can be inserted over and supported by the meat stuffing horn. In use as the meat is extruded the net is pulled off the casing tube (de-shirred) so that it expands and encases the meat. Shining the net allows a large length of net to be loaded onto the fixed length casing tube. When the tube runs out of netting the stuffing machine must be stopped or paused whilst a new (preshirred) casing tube is loaded. Thus, the netting is typically tightly packed to maximise the time between stoppages. Typically shirring of the netting onto the casing tube is performed shortly (ie minutes or hours) before use to minimise the time (or duration) that the netting is kept in a stretched form prior to use, as storage of the netting in stretched configuration tends to reduce its performance in use around a meat product. The size of the tube is limited by the maximum diameter of the rigid netting, or maximum stretched diameter for elastic netting.
Shining arrangements are efficient for netting arrangements. However, some films, and in particular collagen films, are fragile and thus difficult to apply using shining arrangements. This creates problems with providing double casings, as rough treatment can lead to tearing of the collagen film as it is placed over the meat resulting in wastage of meat product.
One arrangement used to double case a meat product as it is extruded is to use a flat collagen film stored on a roll and a means for shaping and wrapping the film around the meat stuffing horn as the meat is extruded through the meat stuffing horn. Shined netting on a casing tube is placed over the meat stuffing horn and shaping and wrapping means, so that the wrapped meat is then encased with the netting to double case the meat product. The diameter of the collagen as the meat is extruded is similar to the diameter of the meat horn and thus the collagen is required to radially expand as it wraps and encases the meat. One method to facilitate this radial expansion is to introduce longitudinal folds or pleats in the collagen. As meat is extruded this pressure pushes the folds outward allowing radial expansion to an expanded diameter (ie the collagen has a reduced diameter on the horn or tube and expands to some nominal maximum diameter). However, one problem with the use of longitudinal folds is that collagen is delicate and can be sticky (especially when wet), and so that as the folds expand to increase the radius, the two sides of a fold can catch on each other preventing free expansion of the fold. In this case pressure mounts on the fold from the filling of meat, leading to tearing of the delicate collagen film. This creates wastage of the collagen, film, netting, meat, and operator time.
There is thus a need to provide an improved apparatus for encasing meat products in a double casing comprising a film and a net, or to at least to provide a useful alternative to current arrangements.